Optical Transport Network (OTN) is defined inter alia in ITU-T recommendation G.709 “Interfaces for the optical transport network” (February 2012) and G.798 “Characteristics of optical transport network hierarchy equipment functional blocks” (December 2012), the contents of which are incorporated by reference. Various protection schemes are often employed to protect customer traffic including line protection (e.g., Automatic Protection Switching (APS)) and/or mesh protection (e.g., through a control plane) to meet the service level agreements (SLAs). Additionally, network operators want to be able to provide on-demand flexible services to support emerging cloud applications. All this requires that OTN traffic at various Optical channel Data Unit level k (ODUk) rates, with k=0, 1, 2, 3, 4, flex, C2, Cn, etc., be dynamically provisioned or de-provisioned, preferably in real-time for most cases. In the case of protection schemes that use shared bandwidth resources, for example, APS M:N (N is number of work lines and M shared protection lines) or mesh-restorable Subnetwork Connections (SNCs) or Label Switched Paths (LSPs), the dynamic provisioning and de-provisioning has to be fast enough to satisfy the sub 50 ms switching time requirements.
The real-time provisioning of ODUk/j connections is a time-consuming operation that can involve multiple steps before end-to-end service is set up or restored from a previous failure. Some of the issues that could slow down provisioning are as follows. First, Optical channel Transport Unit level k (OTUk) signals can experience glitch due to a reference clock change when the underlying ODUk layer transitions from a connection (pass-through) mode to a trail-terminating mode (or vice-versa). This glitch, when seen at the other end might trigger another protection switch resulting in multiple provisioning events. Second, in situations where new provisioning does not match the current provisioning in hardware. For example, if a new request is to provision an ODUj client rate on an interface that was previously prepared for ODUk (where j<k) signals. Now the provisioning will have to, in real time, first delete the ODUk connection provisioning from hardware and then set it up for a trail termination provisioning. The ODUk can be a High Order (HO) connection whereas the ODUj can be a Low Order (LO) connection.
The real-time provisioning can be sped up if a target line is already preconfigured correctly; thereby obviating the need to do certain time-consuming steps like mode change and eliminating all unnecessary side effects like OTN signal glitch. Thus, it would be advantageous to implement adaptive preconfiguration in OTN networks.